I have a late 2008 model Black MacBook (2.4ghz with 4GB of RAM) and am considering getting a new air (probably the 13.3" with 2GB of RAM and 128GB SSD). I really don't need Harddrive space or DVD Drive, so the trade-off is fine. But is this is a decent upgrade? Am I just going to get a small 'bump' or will it feel like a big enough upgrade?